Building out tf2_nodejs

[IanTheEngineer]

As pointed out in RethinkRobotics-opensource/rosnodejs#63 rosnodejs will benefit from a larger set of ROS tools that rospy and roscpp users employ regularly. To start, let's build out a NodeJS implementation of tf2. tf2_ros Python includes:

• transform_broadcaster
• transform_listener
• static_transform_broadcaster
• buffer_interface
• buffer_client
• buffer

[chris-smith]

Do we need to expose BufferInterface? It's the base class of BufferClient and Buffer

[chfritz]

For anyone looking at this package for TF support in rosnodejs: I've create a new package for that: https://github.com/luminrobotics/tf-rosnodejs. I started it not knowing about this one, but I think it might have a few advantages and is slightly more complete at this point, though definitely still work-in-progress. I wanted to avoid using the rather heavy three library (24.1 MB), so I'm just using a very light-weight vector implementation and the quaternion package (78.6 KB) to compute and apply transforms.